The Behavioral Core will serve all individual Projects proposed in this application. In addition to the supervision of husbandry for all animals to be used in the Projects, there are a number of behavioral test procedures that are common to all Projects and these will be conducted in the Behavioral Core. This includes initial behavioral testing to quantify traits that are thought to contribute to vulnerability to addiction, including the propensity to attribute incentive salience to reward cues (measured by Pavlovian approach to reward cues) and the propensity to make impulsive actions (measured by premature responses on a 2-choice serial reaction time task). In addition, drug self-administration testing will be conducted in the Behavioral Core, when feasible and appropriate. The implementation of the Behavioral Core will insure a level of quality control and standardization that will significantly reduce variance and facilitate the comparison of results across individual Projects.